Returning information for other databases now requires privileges For version 12 and earlier databases, you did not need any permissions to execute the following system procedures and functions to return information for any database.
[...]
* DB_EXTENDED_PROPERTY function [System]
[...]

With 12.0.1.4403, I can confirm that behaviour: A restricted user with no particular privileges connected to his database 0 (db_id 0) can query the properties of another database 1 (although he is no user there at all), such as